Syringe

ABSTRACT

A syringe is disclosed. The syringe may include a syringe body with a fluid chamber, the syringe body having a distal end and a proximal end, with an extrusion opening at the proximal end; a dividing wall disposed within the fluid chamber, defining a first fluid chamber and a second fluid chamber, the first fluid chamber and the second fluid chamber in communication with the extrusion opening; a first plunger disposed in a distal end of the first chamber, the first plunger including a first locking mechanism configured to prevent the first plunger from sliding away from the proximal end of the syringe body, when the first plunger is in a first initial position and the second plunger is being depressed; and a second plunger disposed in a distal end of the second chamber, the second plunger including a second locking mechanism configured to prevent the second plunger from sliding away from the proximal end of the syringe body when the second plunger is in a second initial position and the first plunger is being depressed.

RELATED APPLICATIONS

This application is a divisional of U.S. patent applications Ser. No.12/968,576, now U.S. Pat. No. 8,961,474, which claims priority to andthe benefit of U.S. Provisional Patent Application No. 61/292,370, filedon Jan. 5, 2010, the entire disclosure of each of these documents beingincorporated herein by this specific reference.

BACKGROUND

A number of medical applications require the injection of significantamounts of material. For example, one such application is the injectionof dermal fillers to correct facial wrinkles or folds. In such aprocedure, a possibly significant quantity of dermal filler material isinjected under the skin using a syringe. In addition, the materialinjected may have a higher viscosity than the substances typicallyinjected by syringe. For example, some dermal fillers may include gels,such as a gel made of hyaluronic acid. Traditional syringes and theplunger rods used with such syringes present a number of problems whenused for such applications. For instance, in order to accommodatesignificant volumes of material, such syringes must typically haveeither a large length or cross-sectional area. Syringes with largercross-sectional areas are often not practical, however, because theextrusion force required when operating a syringe increases with thecross-sectional area, this may be particularly problematic wheninjecting viscous fluids. Increasing the length of a traditionalsyringe, however, may significantly increase the overall length of thedevice, as a longer plunger may also need to be used, which may reducethe user's comfort and control during use. Accordingly, exampleembodiments provide improved syringe and plunger devices which mayaddress a number of the shortcomings of traditional devices.

SUMMARY

Example embodiments described herein provide a syringe, which mayinclude a syringe body with a fluid chamber, the syringe body having adistal end and a proximal end, with an extrusion opening at the proximalend; a dividing wall disposed within the fluid chamber, defining a firstfluid chamber and a second fluid chamber, the first fluid chamber andthe second fluid chamber in communication with the extrusion opening; afirst plunger disposed in a distal end of the first chamber, the firstplunger including a first locking mechanism configured to prevent thefirst plunger from sliding away from the proximal end of the syringebody, when the first plunger is in a first initial position and thesecond plunger is being depressed; and a second plunger disposed in adistal end of the second chamber, the second plunger including a secondlocking mechanism configured to prevent the second plunger from slidingaway from the proximal end of the syringe body when the second plungeris in a second initial position and the first plunger is beingdepressed.

In some example embodiments, the first locking mechanism may include afirst locking wing formed at a proximal end of the first plunger; and afirst groove formed in the distal end of the first fluid chamber; wherethe first locking wing may be positioned to engage in the first groovewhen the first plunger is in the first initial position.

Some example embodiments may also include a third locking mechanismconfigured to prevent the first plunger from sliding away from theproximal end of the syringe body, when the first plunger is in a firstfinal position and the second plunger is being depressed; and a fourthlocking mechanism configured to prevent the second plunger from slidingaway from the proximal end of the syringe body, when the second plungeris in a second final position and the first plunger is being depressed.

In some example embodiments, the third locking mechanism may include athird locking wing formed at a distal end of the first plunger; and athird groove formed in a distal end of the first fluid chamber; wherethe third locking wing may be positioned to engage in the third groovewhen the first plunger is in the first final position.

In some example embodiments, the first groove may be the third groove.In other example embodiments the first groove may be distinct from thethird groove. In still other example embodiments, the first locking wingmay be a directional locking wing or the third locking wing may be adirectional locking wing.

In some example embodiments, the first fluid chamber and the secondfluid chamber may have a semi-circular cross-section. In other exampleembodiments, the first fluid chamber and the second fluid chamber mayhave a rectangular cross-section.

Other example embodiments may provide a syringe, which may include asyringe body with a fluid chamber, the syringe body having a distal endand a proximal end, with an extrusion opening at the proximal end; anouter plunger disposed in the distal end of the fluid chamber, the outerplunger having a bore running from a distal end to a proximal end; andan inner plunger slidably disposed in the bore.

Some example embodiments may also include a first locking mechanismconfigured to prevent the inner plunger from sliding relative to thesyringe body when the inner plunger is in an initial position and theouter plunger is being depressed.

Some example embodiments may also include a first slot in the outerplunger, extending a portion of the length of the outer plunger from thedistal end to the proximal end; where the first slot may be configuredto allow the outer plunger to slide relative to the inner plunger andthe syringe body when the first locking mechanism is engaged.

In some example embodiments, the locking mechanism may include a firstlocking arm disposed on the inner plunger near a proximal end of theinner plunger; and a first groove disposed within the syringe body nearthe distal end of the syringe body; where the first locking arm may beconfigured to engage in the first groove, when the inner plunger is inthe initial position, passing through the first slot.

Some example embodiments may also include a second locking mechanism,configured to prevent the outer plunger from sliding relative to thesyringe body when the outer plunger is in a final position and the innerplunger is being depressed.

In some example embodiments, the second locking mechanism may include afirst locking tab disposed on the outer plunger near the distal end ofthe outer plunger; and a second groove disposed within the syringe bodynear the distal end of the syringe body; where the first locking tab maybe configured to engage in the second groove, when the outer plunger isin the final position.

In some example embodiments, the first groove may be the second groove.In other example embodiments, the inner plunger and the outer plungermay have circular cross-sections. Some example embodiments may alsoinclude an outer plunger tip attached to the outer plunger; and an innerplunger tip attached to the inner plunger; where the inner plunger tipmay be shaped to fit within a hole passing through the outer plungertip.

In some example embodiments, the outer plunger tip may have a ringshape; and the inner plunger tip may have a disk shape.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more readily understood from a detaileddescription of example embodiments taken in conjunction with thefollowing figures:

FIG. 1 illustrates an example dual-chamber/dual-plunger syringe inaccordance with an example embodiment.

FIG. 2 illustrates an example dual-chamber/dual-plunger syringe inaccordance with an example embodiment.

FIGS. 3A-3C illustrate transparent views of an exampledual-chamber/dual-plunger syringe in accordance with an exampleembodiment.

FIG. 4 illustrates a cross-sectional view of a dual-chamber/dual-plungersyringe in accordance with an example embodiment.

FIG. 5 illustrates a detailed view of an exampledual-chamber/dual-plunger syringe in accordance with an exampleembodiment.

FIG. 6 illustrates a disassembled view of an exampledual-chamber/dual-plunger syringe in accordance with an exampleembodiment.

FIGS. 7A-7C illustrate an example single-chamber/dual-plunger syringe inaccordance with an example embodiment.

FIGS. 8A-8C illustrate an example single-chamber/dual-plunger syringe inaccordance with an example embodiment.

FIGS. 9A-9C illustrate an example single-chamber/dual-plunger syringe inaccordance with an example embodiment.

FIG. 10 illustrates a disassembled view of an examplesingle-chamber/dual-plunger syringe in accordance with an exampleembodiment.

DETAILED DESCRIPTION

Example embodiments of the invention generally relate to a new syringesystem designed to dispense large volumes of fluid, while minimizing theforce of extrusion and length of the device. Such example embodimentsmay, for example, be used in the administration of gels that can havecosmetic or medical applications.

Most current syringes are designed to dispense low viscosity fluidsthrough a fine needle with minimum extrusion force. Higher viscosityfluids (e.g. dermal fillers) can also be dispensed with the currentdesign, however at a considerably higher extrusion force. This canresult in injection fatigue, as physicians are often required to performnumerous injections on a daily basis. In some other instances, highextrusion force can result in needle disengagement and possibly patientinjury. Example embodiments, however, provide a syringe device reducesthe extrusion force required, e.g., to extrude highly viscous fluidthrough a fine needle, while maintaining the same fill volume.

As an initial matter, the extrusion force required to maintain aconstant flow of a Newtonian fluid through a tube with a constantcircular cross-section is governed by the Hagen-Poiseuille equation:

${F = {{{A \cdot \Delta}\; P} = {{\pi \; {r^{2} \cdot \frac{8\; \mu \; {LQ}}{\pi \; r^{4}}}} = \frac{8\; \mu \; {LQ}}{r^{2}}}}},$

where:

ΔP is the pressure drop required to maintain a constant volumetric flowrate Q,

μ is the dynamic viscosity,

L is the length of the tube, and

r is the radius of the tube.

This general equation can be applied to a needle of length L_(n) andradius r_(n)

${F_{n} = \frac{8\; \mu \; L_{n}Q}{r_{n}^{2}}},$

This force must be applied to a cross-sectional area in the entrance ofthe needle to maintain a constant flow rate Q. The corresponding forceon a cross-sectional area in the syringe can be calculated by assumingzero pressure drop in the syringe and equating the pressure in theentrance of the needle with the pressure in the syringe:

$F_{s} = {{F_{n}\frac{A_{s}}{A_{n}}} = \frac{8\; \mu \; L_{n}{QA}_{s}}{\pi \; r_{n}^{4}}}$

where:

A_(s) is the cross-sectional area of the syringe, and

A_(n) is the cross-sectional area of the needle.

This is a simplified equation that assumes that the bottleneck of theprocess is the needle (where the majority of the extrusion energy islost) and neglects entrance losses as the flow transitions from thesyringe to the needle as well as losses in the syringe. According tothis equation the extrusion force for a given flow rate Q isproportional to the length of the needle L_(n), the viscosity of thefluid μ, and the cross sectional area of the syringe A_(s), andinversely proportional to the 4th power of the needle radius r_(n).

For a given fluid, needle, and flowrate, the only parameter that is leftto control the extrusion force is the syringe cross-sectional area.Minimizing that parameter can reduce the force required to extrude aviscous solution through a fine needle. However, there is a limit on howmuch this area can be reduced, which is primarily determined by the fillvolume of the syringe. As the syringe diameter decreases, the length ofthe syringe has to increase to accommodate the fixed volume of fluid.Increasing the length of the syringe, however, can result in practicalissues, e.g. reduced functionality, ergonomics considerations, and lesscontrol over the needle that can not only cause physician discomfort,but ultimately affect the patient's safety.

Example embodiments may resolve these problems by, for example,providing dual/multi-chamber and/or dual/multi-plunger devices designedto reduce the force required to extrude a fluid through a fine needlewhile maintaining the same fill volume and length as a conventionalsyringe. In some example embodiments, such an effect is achieved bysplitting a single syringe chamber into two or more chambers of equal ordifferent cross-sectional areas and attaching one plunger to eachchamber. The fluid is then extruded by applying force to the firstplunger until it moves all the way through the first chamber and locksin the end position and then by applying force to the second plunger andso on until all the fluid is dispensed. In such example embodiments, allchambers merge into a single needle at the end of the device proximal tothe point of injection (the terms proximal and distal, as used herein,are to be understood in relation to the point of injection during use).In other example embodiments, a single chamber may be provided with adual/multi-plunger set-up, achieving a similar reduction in extrusionforce.

An example syringe and plunger device in accordance with an embodimentis shown in FIG. 1. As illustrated, the example device may have asyringe body 101 and a plurality of plungers 102, 103. The syringe body101 may be shaped substantially like a conventional syringe. Forinstance, the syringe 101 may be cylindrical, may have a proximal end,which may include an opening for extruding the injectable materialcontained in the syringe, and may also include an attachment point forattaching a needle 104, e.g. a luer, or may have an integrated needle104. In addition, the syringe body 101 may also include finger grips105, which may be used like the finger grips of a convention syringe,allowing a user to apply pressure to the plunger rods 102, 103.

In example embodiments, the syringe chamber may be divided into multiplechambers by a dividing wall. For example, the depicted syringe body 101may be divided into two chambers, where each chamber may have ahalf-cylinder shape, though other shapes are also usable, e.g., chamberswith the shape of a rectangle or other polygon, or of an oval, may alsobe used. The dividing wall may extend the length of the syringe 101 upto the point at which it meets the needle opening, or syringe luer, etc.In such embodiments, a plunger 102, 103, shaped to match the chambers,may be inserted into to the distal end of each chamber. Such plungersmay be shaped generally in the form of a rod, and may have a plunger tipat a proximal end and a thumb grip at a distal end.

It is noted that FIG. 1 illustrates both plungers 102, 103 in theirinitial positions. That is, neither plunger 102, 103 has been pushedinto the syringe body 101 at this point. FIG. 2 illustrates the finalposition of the device once all the material has been extruded. To usethe device, a force may be applied to the first plunger 102 until allmaterial in the first chamber is extruded and the plunger is locked inthe final position. Force may then be applied to the second plunger 103until all the material in the second chamber is extruded through thesame needle 104 and the plunger 103 is locked in the final position.

FIGS. 3A-3C illustrate an example embodiment in use in more detail. Asan initial matter, the dividing wall 301, and the two chambers 302, 303may be seen in the transparent view. In the initial state (FIG. 3A) bothplungers 102, 103 are fully extended out of the distal end of thesyringe body 101. A user may then apply a force to one of the plungers102, 103, e.g. plunger 103, such as shown in FIG. 3B. As the user pushesthe first plunger 103 towards the proximal end of the syringe body 101,material is extruded from the needle 104. Once the first plunger 103 hasbeen pushed its entire length, the user may then begin pushing thesecond plunger 102, and may push that plunger 102 into the syringe body101 until the syringe body 101 has been emptied, as shown in FIG. 3C.

In order to facilitate this process, a number of locking devices may beprovided. Such locking devices may be necessary to the operation of thesyringe device because, during use, the force exerted on each plunger102, 103 may result in a force tending to push the other plunger 102,103 out of the syringe body 101. These forces may be understood withreference to FIG. 4.

First, it is noted that, because, in some embodiments, both chambers302, 303 of the syringe use the same needle 104, the two chambers 302,303 are not fully separated, but, rather, are in communication at theproximal end of the syringe. Thus pressure applied to the material inthe first chamber 303 is also experienced in the second chamber 302.Locking mechanisms may therefore be provided to keep the plungers 102,103 in place when experiencing such forces.

For instance, as shown in FIG. 4, a force A is being applied to thelower plunger 103 by a user. As a result, the fluid in the lower chamber303 exerts a force B to the needle 104, which in turn causes fluid 401to be extruded through the needle 104, as intended. However, because thetwo chambers 302, 303 are in communication, the fluid also applies forceD to the upper plunger 102. If the upper plunger 102 were free to slide,it could be pushed out of the syringe body 101. Therefore, a lockingmechanism may be supplied to prevent the unused plunger from moving.

The locking mechanism may take any appropriate form. For instance, a tab402, or multiple tabs, may be provided on the plunger rod 102, 103, nearthe distal end of the plunger rod 102, 103. For example, as illustratedin the drawings, two tabs 402 may be located on the plunger rods 102,103, opposite from one another. Such tabs 402 may be made of anymaterial, and may be an integral part of the plunger rod 102, 103 or maybe attached to the plunger rod 102, 103. In addition, slots 403 may beprovided in the body of the syringe 101, corresponding to the positionof the tab or tabs 403, when the plungers 102, 103 are in their initialposition. For instance, a slot 403 may be provided in the inner surfaceof the chamber 302, 303 in which the plunger 102, 103 is inserted, nearthe distal end of the chamber. In the initial state, the tab 403 may beengaged in the slot 403, and may prevent the plunger 102, 103 fromsliding out of the syringe body 101.

In some example embodiments, other locking mechanisms may be employed.For example, a tab and slot lock may again be used. However, the tab maybe located on the syringe body while the slot is formed in the plungerrod. Alternatively, a tab may again be provided on either element, whileanother tab or ridge is provided on the corresponding element. Forinstance, a tab may be provided on the plunger rod, and a second tab maybe provided on the syringe. In such a case, the initial position of theplunger rod tab would be closer to the proximal end of the syringe thanthe tab or ridge on the syringe body.

In addition, the locking mechanism may be structured to be directional.For example, a tab and slot lock may be provided in which both the taband the slot are triangular, or wedge shaped. For example, a tab formedon the plunger rod may have a triangular cross-section, where the tabjoins the plunger rod at an acute angle closer to the proximal end,while the tab joins the plunger rod at a right angle further from theproximal end. Using such a locking mechanism, less force may be neededto push the plunger towards the needle than is required to push theplunger away from the needle when the lock is engaged.

Such locking mechanisms may be provided for both plungers 102, 103, forjust one plunger, or for any number of plungers in example embodimentsemploying more than two plungers. In addition, similar lockingmechanisms may be provided for locking plungers in their final position.

For instance, a second tab 501, illustrated in FIG. 5, may be providedon a plunger rod 102, 103 located closer to the distal end. Such a tab501 may be shaped to engage with the same slot 403 used to engage a tab402 locking the plunger 102, 103 in an initial position. Alternatively,a different slot may be used. Again, any locking mechanism may beemployed. For instance, as above, a slot may be provided on the plungerrod 102, 103 while a tab is provided on the syringe body 101.

In FIG. 5, one of the two plungers 102 has been pushed entirely into thesyringe 101. In this position, two locking tabs 501 disposed on eitherside of the plunger rod 102 have engaged in locking slots 403 in thesyringe body 101. In this state, the plunger rod 102 will resist furthersliding. As can be seen, the other plunger rod 103 has similar lockingtabs 501. If the second plunger 103 is pushed slightly further thelocking tabs 501 will enter the syringe body 101, align with slots 403provided in its chamber 303, and, therefore, lock the plunger 103 in itsfinal position as well. At that point all of the material in bothchambers 302, 303 may have been extruded.

Components of a dual half-cylinder embodiment are shown in FIG. 6.Illustrated are a dual half-cylinder chamber syringe 101, one of twohalf-cylinder shaped plunger rods 102, and one of two semi-circularplunger tips 601. As discussed above, the plunger rod 102 may have anumber of locking wings or tabs. For instance, the illustrated plungerrod 102 has a first locking wing 402 near the proximal end, which locksthe plunger 102 in its initial position, and another locking wing 501near the distal end, which locks the plunger rod 102 in its finalposition.

Such example devices may allow for an approximately 50% reduction inextrusion force, as compared to a standard syringe ofsingle-chamber/single-plunger design with the equivalent volume, outerdiameter, and length. If necessary, a further reduction in extrusionforce can be accomplished by dividing the single chamber into more thantwo chambers and adding an additional number of corresponding plungers.

Another example embodiment is illustrated in FIG. 7. The exampleembodiment again provides a syringe body 701 and two or more plungers702, 703. In the example embodiment, a syringe 701 with a traditionalfluid chamber is used, undivided by a dividing wall. Again two plungers702, 703 are provided, in the example, an outer 702 and an inner plunger703. The inner 703 and the outer 702 plungers may be integrated so thatthey can slide along their common axis, but this motion may be limitedbetween two extreme points. Such plungers 702, 703 may again beessentially in the form of a rod, and may have a plunger tip and a thumbgrip. In addition, such plungers 702, 703 may also have anycross-sectional shape. For instance, the plungers 702, 703 areillustrated in the figures with a circular cross-section; however, theymay also be elliptical, or have the shape of a rectangle or otherpolygon.

The example embodiment may again be used by pushing one plunger 702, 703at a time into the syringe body 701, e.g., the outer plunger 702 may bepressed into the syringe body 701 and then the inner plunger 703 may belikewise pressed into the syringe 701. It is noted that, as in theprevious example, exerting a force on the outer plunger 702 may tend topush the inner plunger 703 of the syringe. Accordingly, exampleembodiments may provide for locking mechanisms to prevent such movement.

As shown in the figure, one or more slots 704 may be provided in theouter plunger rod 702, in the example two slots 704 are providedopposite each other. The slots 704 may extend from a point near thedistal end of the plunger shaft, to a point near the proximal end. Inaddition, one or more locking arms 705 may be provided on the innerplunger rod 703. Again, two locking arms 705 are provided in theillustrated example. A locking groove 706 may be provided in the syringebody 701 which is configured to engage the locking arms 705, when theinner plunger 703 is in the initial position. In order to do so, thelocking arms 705 may pass through the slots 704 in the outer plunger rod702. It is noted that, because the slots 704 may extend along the lengthof the outer plunger rod 702, the plunger rods 702, 703 may be free toslide relative to each other. It is also noted that, because it is notpossible to use the inner plunger 703 first, in the example embodiment,the inner plunger 703 need not be supplied with a locking mechanismpreventing movement from its final position. However, in otherembodiments such a mechanism may be supplied.

Also as noted above, force exerted on the inner plunger 703 will tend toforce the outer plunger 702 out of the syringe 701 as well. Accordingly,the outer plunger 702 may also be provided with a locking mechanism. Forexample, the outer plunger rod 702 may include one or more locking arms707, positioned near the distal end of the plunger rod 702. Forinstance, it may be equipped with two locking arms 707, e.g., at a 90°angle to the locking arms 705 of the inner plunger 703. These lockingarms 707 may engage with the same locking groove 706 formed in thesyringe 701, or in another groove. Again, as the outer plunger 702 mustbe used first in the initial configuration, there may be no need to lockit in its initial position. However, some embodiments may providelocking arms, or other mechanisms, for that purpose.

FIGS. 7A-9C illustrate the use of such an example embodiment. In FIGS.7A-7C, the plungers 702, 703 are in their initial position, asdescribed. From this position a user may apply a force to the outerplunger rod 702, pushing it into the syringe body 701 and extrudingmaterial from the needle 708. Force may be applied to the outer plunger702 until it slides all the way to the other end of the syringe chamberand locks into its final position through the two locking arms 707, inthe position shown in FIGS. 8A-8C. The inner plunger 703 may have beenheld in place by its two locking arms 705, as the outer plunger rod 702was pressed into the syringe 701, resisting the force exerted by thefluid in the chamber. The outer plunger slots 704 allow for the innerplunger locking arms 705 to engage the syringe groove 706 while theouter plunger moves 702.

Once the outer plunger 702 locks into its final position, force may beapplied to the inner plunger 703 until the remaining material isextruded. Once the inner plunger 703 is pushed all the way into thesyringe body 701, all of the material in the syringe will have beenextruded, and the device will be in its final position, shown in FIG.9A-9C.

FIG. 10 illustrates example components of such example embodiments, indetail. The figure illustrates a single cylindrical chamber syringe 701,an outer plunger 702 with two slots 704 and two locking arms 707, anouter plunger tip 1001, an inner plunger 703 with two locking arms 705,and an inner plunger tip 1002. As explained above, when assembled, theouter plunger 702 fits into the syringe 701, while the inner plunger 703fits into the outer plunger 702. The plunger tips 1001, 1002 nestsimilarly. For example, the outer plunger tip 1001 may be shaped in theform of a ring, while inner plunger tip 1002 may be shaped in the formof a disk, able to fit within the outer plunger tip 1001.

Such example embodiments may also allow for an approximately 50%reduction in extrusion force, as compared to a standard syringe ofsingle-chamber/single-plunger design with the equivalent volume, outerdiameter, and length.

In the preceding specification, the present invention has been describedwith reference to specific example embodiments thereof. It will,however, be evident that various modifications and changes may be madethereunto without departing from the broader spirit and scope of thepresent invention. The description and drawings are accordingly to beregarded in an illustrative rather than restrictive sense.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the invention are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements.

The terms “a,” “an,” “the” and similar referents used in the context ofdescribing the invention (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.Recitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember may be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. It isanticipated that one or more members of a group may be included in, ordeleted from, a group for reasons of convenience and/or patentability.When any such inclusion or deletion occurs, the specification is deemedto contain the group as modified thus fulfilling the written descriptionof all Markush groups used in the appended claims.

Certain embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Ofcourse, variations on these described embodiments will become apparentto those of ordinary skill in the art upon reading the foregoingdescription. The inventor expects skilled artisans to employ suchvariations as appropriate, and the inventors intend for the invention tobe practiced otherwise than specifically described herein. Accordingly,this invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that may be employed are within the scopeof the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention may be utilized inaccordance with the teachings herein. Accordingly, the present inventionis not limited to that precisely as shown and described.

We claim:
 1. A syringe, comprising: a syringe body with a fluid chamber,the syringe body having a distal end and a proximal end, with anextrusion opening at the proximal end; a fluid chamber in communicationwith the extrusion opening; an outer plunger slidably disposed in thefluid chamber; and an inner plunger slidably disposed in the outerplunger; wherein the inner plunger includes a first locking mechanismconfigured to prevent the inner plunger from sliding away from theproximal end of the syringe body, when the outer plunger is beingdepressed to eject a dermal filler from the fluid chamber.
 2. Thesyringe of claim 1 further comprising: a second locking mechanismconfigured to prevent the outer plunger from sliding away from theproximal end of the syringe body, when the outer plunger is in a firstposition and the inner plunger is being depressed to eject a dermalfiller from the fluid chamber.
 3. The syringe of claim 1 wherein theouter plunger and the inner plunger share a common axis.
 4. The syringeof claim 1 wherein the outer plunger includes a slot and the innerplunger includes a locking arm engaged with the slot.
 5. The syringe ofclaim 1 wherein the outer plunger includes two slots opposing oneanother, and the inner plunger includes two locking arms engaged withthe slots.
 6. The syringe of claim 4 further comprising a locking groovein the syringe body configured to engage the locking arm.
 7. The syringeof claim 5 further comprising a locking groove in the syringe bodyconfigured to engage the locking arms.